Method for producing tin-coated copper tubes



Sept. 26, 1944. R UPTQN 2,358,892

METHODS FOR PRODUCING TIN-COATED COPPER TUBES Filed Dec. 9, 1942 I fly film/'7 0m 4 I v a Patented Sept. 26, 1.944

. METHOD FOR PRODUCING TIN-"COATED COPPER TUBES Austin R; Upton, Hamden, Conn., assignor 'to Western" Cartridge Company, Conn., a corporation of Delaware New Haven, 7

Application December 9, 1942, Serial in). 468,372

"4 Claims.

The present invention relates to improvements in methods whereby tubes of copper may beproduced with coatings oftin.

One of the objects of the present inventionis to provide a superior low-cost method for producing tin-coated copper tubes.

Another object, of the present invention is 'to provide a superior method whereby a copper tube may be provided with a consolidated coating of tin for purposes of improving the corrosion resistance or for imparting other desirable properties to the resultant tin-coated copper tube.

A furtherobiect of the present invention is to provide a superior method whereby copper tubes may be produced which are, provided with extremely-thin but adherent, continuous and consolidated tin coatings.

With the above and other objects in view, as

- will appear to those skilled in the art from the ratus suitable for carrying out the present invention, and showing the tin-coated copper billet or blank in place in the die preparatory to the impacteextrusion operation Fig. 3 is a view corresponding to Fig. 2 but showing the elements in the positi'onswhich they assume during the impact-extrusion operation; and

Fig. 4 is a broken perspective view partly in section of a tin-coated copper tube produced in accordance with the present invention.

In the preferred mode of carrying out the present invention, a cylindrically-contouredcupshaped blank or billet I0 is provided which has -a relatively-thick annular side-wall H and a rela-- The said tively-thin bottomor end-wall l2. billet It! may be formed of commercially-pure copper or a high-copper alloyresponsive to impact-extrusion, and is preferably so formed that its grain structure is oriented in the direction of its longitudinal axis. The billet or blank HI is provided with a coating of tin I 3 which preferably covers both the interior and exterior of the said blank and which may be applied thereto by dipping the blank in a molten bath of tin in a manner as will presently be described.

In order to properl bond the tin-coating to the copper blank or billet so that the said coating will be properly jointly extrudable with the copa suitable cavity, such as thecavity H formed in per of the blank itself,,-t hesaidblank, after proper cleaning and fluxing, is immersed ma bath of molten tin. By thuscoating the copperbase billet or blank not only is an adequately thick coating-provided for later thinning, but the said coating is made in effect an integral partof thef-copper-bas'e material; It appears that by the hot-coating step lust referred to, the inner-part' of the tin-coating alloys or amalgamates with the copper of the billet in 'c ontradistinct'ion to a mere surface contact. The alloying or eL rrialga-- mationreferred to, virtually createsa minutelythin bronze (copper and tin) bonding layer between the inner surfaces of the tin-coating and the outer surfacesof the bille'tjor blank; The thickness of the tin-coating I3 is somewhat exaggerated from norm'aljin the accompanying drawing for purposes'of clarity of illustration, but the thickness may be regulated in manners well understood in the art, to provide'a thickness of coating which will eventuateinto the desired thickness of coating on the finished tube when the blank is subjected toimpact-extrusion in a manner as will more fully hereinafter appear.

Following its being provided with a coating of tin such as It, the billet or blank I0 is placed in an extrusion die i 5 and provided at its, lower portion with an extrusion-passage or orifleeit" of circular form in cross, section and ;corresponding in diameter to the desired outsidediameter of the tube to be produced. In conjunction with the die IS, a suitable extrusion punch such as il is employed, which is provided at its lower end. with an integral coaxial extrusion-mandrel l8 having a diametercorresponding to the desired. interior diameter of the tube to be produc'ed'andf also substantiallyv correspondin to the interior diameter of billet l0 and'its' coating I3. I

By means of any suitable impact-extrusion press, the extrusion-punch l 1- is caused to dew scend with a hammer-like blowto cause' its'extrusi'on-mandrel l8 to enter the open upper end of the cup shapedbillet or blank land its tin coating i 3 so as to punch through the'thin bottom-wall l2 and'to extend through the extrusiona passage or orifice 18 in the extrusion-die [5. The diameter of the extrusion-mandrel l8 of the extrusion-punch I] is preferably such as to substantially correspond to the interior diameter of the coated billet l0, and when the said mandrel enters the extrusion-passagelfi in the extrusiondie l5, it will occupy a central position therein.

After the lower portion ofsthe extrusion-mandrel" l8 has penetrated the end-wall i 2 of the billet or blank l0 and has entered the extrusionpassage it in the extrusion-die l5, theextrusionshoulder IQ of the extrusion punch ll w'illen gage with the upper portion of the billet l0 and will compress or extrude the billet I0 and its al- 2 assaaaa loyed tin-coating l l in such manner that the metal of both the said billet i and coating II has but one channel escape, namely, that through the annular ring-like space now existing between the periphery of the extrusion-mandrel I! and the surface of the extrusion-passage l6. As the punch I1 continues to descend, the copper-base metal of the billet III will be extruded through the extrusion-passage l6 and around the extrusionmandrel l8 into the form of a thin-walled copperbase tube schematically shown in Figs. 3 and 4. At the same time that the copper of the billet II is extruded, the tin of the coating 13 will also be extruded in situ while bonded on the said copper-' base metal and proportionately thinned to provide the copper-base tube 20 with an outer tincoating 2| and; an inner tin-coating 22. The stroke of the punch i I may be continued until its extrusion-shoulder l9 engages with the bottom of the cavity H in the extrusion-die i5, and normally the extruded metals will have such impetus, due to the rapidity of the stroke of the said punch ll, that the said extruded metals will strip themselves, so to speak, out of the extrusion-passage l6 and oil from the extrusion-mandrel l8.

7 The extrusion-punch i! may now be withdrawn and restored to substantially the position in which it is shown in Fig. 2, preparatory to the insertion of another tin-coated billet into the cavity I4 and preparatory to another cycle of operations.

During the process of impact-extrusion as above described, the relatively-thick tin-coating IS on the billet or blank I, even though relatively-porous and lacking in desired density, will be consolidated and densiiied as it is converted into the respective outer and inner coatings 2i and 22 without, however, rupturing the bond between themselves and the copper-base metal.

By means of the present invention, copper-base metals may be economically converted into thinwalled tubes having one or more coatings of tin. by the simple expedient of first providing the billet or blank with a relatively-heavy alloyed or amalgamated coating of tin and then simultaneously thinning the metal of the blank itself, together with its coating. The resultant product possesses a hard, dense and substantially-nonporous coating which is free of breaks and interruptions. The impact-extrusion operation above described "is carried on while the billet, the coating and the extrusion apparatus are at room temperature, with the result that though considerable heat is momentarily developed during the extrusion operation, the time factor is of such short duration that the resultant thin-walled tube (which may have a wall-thickness or the order of .005") is adequately work-hardened to enable it to withstand collapse and distortion stresses to a marked deg ee. a

The invention may be carried out in other spe cinc ways than those herein set'forth without departing from the spirit and essential characteristics of the invention, and the present embodlments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced-therein.

I claim:

1. The improvement in methods for producing tin-coated copper tubes comprising: providing a tube-like billet of copper; providing the interior peripheral portion of the said tube-like billet with a relatively-thick tubular coating of tin partially amalgamated with the copper of the interior peripheral portion or the said billet;

. placing the said tube-like billet with its said pretin-coated copper tubes comprising: providing a tube-like billet of copper; providing both the interior and exterior peripheries of the said tubelike billet respectively with a relatively-thick tubular coating of tin partially amalgamated with the-copper of the said billet; placing the said billet with its said previously-applied tubular coatings in an apertured extrusion-die; and simultaneously subjecting the said copper billet and both its interior and exterior tubular tincoatings to the action of an impact-punch to simultaneously extrude the said tube-like copper billet and its two said tubular coatings of tin through the said apertured die and into tubular form and thinning and consolidating both the said exterior and interior tubular coating of tin while the same are bonded to the copper of the said billet as the latter is extruded.

' 3. The improvement in methods for producing tin-coated copper tubes comprising: providing a cup-shaped billet of copper; providing the interior peripheral portion of the said cup-shaped billet with a relatively-thick tubular coating of tin partially amalgamated with the copper of the interior peripheral portion of the said billet; placing the said cup-shaped billet with its said previously-applied tubular interior, coating in an apertured extrusion-die; and simultaneously subjecting the said cup-shaped copper billet and its interior tubular tin-coating to the action of an impact-extrusion punch to simultaneously extrude the said cup-shaped copper billetand its said interior tubular tin-coating through the said apertured die and into tubular form and thinning and consolidating the said interior tubular tincoating while the same is bonded to the copper of the interior of the said cup-shaped billet as the latter is extruded.

4. The improvement in methods for producing tin-coated metal tubes comprising: providing a cup-shaped billet of copper; providing both the interior and exterior peripheries of the said cup-shaped billet respectively with a relativelythick tubular coating of tin partially amalgamated with the copper ot the said billet; placing the said billet with its said previously-applied tubular coatings in an apertured extrusion-die; and simultaneously subjecting the said copper billet and both of its said tubular tin-coatings to the action of an impact-extrusion punch to simultaneously extrude the said cup-shaped copper billet and both its said inner and outer tubular tin-coatings through the said apertured die and into tubular form and thinning and consolidating both the said interior and exterior tubular tin-coatings while the same are bonded to the copper of the said cup-shaped billet as the latter is extruded.

AUSTIN R. UPI'ON. 

